1. Field of the Invention
The present invention relates to an assembly apparatus for assembling a sub-assembly of a swash plate type fluidic apparatus, such as a compressor, a pump, or the like. In particular, it relates to an assembly apparatus for assembling the sub-assembly in which a plurality of pistons and hemispherical shoes are disposed at predetermined intervals around a swash plate so as to straddle the swash plate which is mounted on a driving shaft.
2. Description of the Prior Art
There are swash plate type fluidic apparatuses. For example, Japanese Unexamined Patent Publication (KOKAI) No. 54-108,008 discloses a swash plate type fluidic apparatus, a double-headed swash plate type compressor for air-conditioning a vehicle. In the compressor, a pair of cylinder blocks are disposed opposingly at the front and the rear, and a swash plate chamber is formed at the connection of the cylinder blocks. The swash plate chamber is communicated with a suction port for a return coolant. The cylinder blocks are enclosed by housings and valve plates at the outer ends, and a suction chamber and a discharge chamber are formed in the housings. The suction chamber and the discharge chamber are communicated with the swash plate chamber. The cylinder blocks are provided with a central shaft hole disposed on a common axis. A driving shaft is inserted into the shaft holes rotatably. A swash plate installed on the driving shaft is accommodated in the swash plate chamber rotatably. Further, the cylinder blocks are provided with a plurality of bores which are disposed parallel around the driving shaft at the front and the rear, and a double-headed piston is inserted into each of the bores reciprocatively. The double-headed pistons are coupled to the swash plate by way of hemispherical shoes. Furthermore, the cylinder blocks are provided with a plurality of suction passages which communicate the swash plate chamber with the suction chambers of the housings, and they are also provided with a discharge passage which communicates the front discharge chamber with the rear discharge chamber.
When manufacturing the swash plate type fluidic apparatus of this kind, it is required that a sub-assembly be assembled by disposing a plurality of the pistons and the hemispherical shoes around the swash plate at predetermined intervals so as to straddle the swash plate. Such an assembly has been carried out conventionally with an assembly jig 90 as illustrated in FIG. 10. The assembly jig 90 includes a body 91 provided with a concavity 91a which is adapted to place a plurality of pistons 81 in a predetermined circumferentially spaced relationship, and a pair of retractable members 92 which are retractable perpendicularly to the body 91 and provided with a concavity 92a adapted to place the piston 81 similarly. In addition, the body 91 and the retractable members 92 are formed in such configurations that they do not interfere with a swash plate 83 installed on a driving shaft 82 at their central regions.
The assembly operation with the assembly jig 90, for instance, assembling a sub-assembly of a double-headed swash plate type compressor provided with 5 cylinders on each of the sides, is carried out as follows. At first, the following component parts are prepared: the swash plate 83 installed on the driving shaft 82 with a predetermined inclination angle, 5 pairs of the hemispherical shoes 84, and 5 pistons 81 provided with a pair of spherical seats 81a. In the pistons 81, the spherical seats 81a are disposed opposingly, and they are adapted to engage the shoes 84 between themselves and the swash plate 83 when the assembly is completed.
After retracting the retractable members 92 of the assembly jig 90, a set of the piston 81 and the hemispherical shoes 84 is disposed in the lowermost part of the concavity 91a of the body 91, and the driving shaft 82 and the swash plate 83 are disposed in the assembly jig 90 with the swash plate 83 inserted between the shoes 84. Further, two sets of a piston 81 and shoes 84 are disposed in the intermediate parts of the concavity 91a of the body 91 with the swash plate 83 placed between the shoes 84. Then, the retractable members 92 are stood upright. Thereafter, another two sets of a piston 81 and shoes 84 are disposed in the uppermost parts of the concavity 92a of the retractable members 92 with the swash plate 83 placed between the shoes 84. Thus, the sub-assembly of the double-headed swash plate type compressor is completed. Finally, the sub-assembly is inserted into front and rear cylinder blocks (not shown), and it is transferred to the subsequent manufacturing process.
However, during the conventional assembly operation, an operator must hold the piston 81 with his hands, and at the same time he must retain the hemispherical shoes 84 in the pair of spherical seats 81a disposed opposingly in the pistons 81 with his fingers as illustrated in FIG. 9. While maintaining these states, he must dispose the five sets of piston 81 and shoes 84 in the assembly jig 91, stand the retractable members 92 upright, and carry out the other required operations. Accordingly, the conventional assembly operation requires quite a skill, and it cannot be carried out quickly so as to shorten the assembly time because it is a manual operation done by an operator.